This invention relates to the field of electrical connectors and more particularly to flexible pin type contacts of the type formed in one piece from thin metal stock for detachable wiping-type engagement with the inside surface of tubular sockets.
To make flexible pin type contacts the practice has been to stamp a number of blanks from a single piece of flat metal stock and then to form each blank into the shape of an individual pin contact. To wipingly engage the inside surface of the tubular socket, each formed contact includes a plurality of forwardly extending elongate arm members. Often a protruding sleeve member is rearwardly formed on each contact so that the contact will come to rest, upon wiping engagement, against the protruding rim of the sleeve member.
During the stamping operation, frequently minute burrs are created along the corner edges of the blank and particularly along the corner edges of what will become the arm members. These burrs can interfere with continuous engagement between the arm members and the inside surface of the socket and thereby adversely affect the reliability of the resultant electrical connection.
One approach used to counteract the creation of these burrs has been to fold the edges of each arm back upon themselves. This folding is performed so that the radius of curvature of the arm in a transverse plane is less than the radius of curvature of the inner surface of the socket thereby elevating the burrs inwardly away from engagement with the inner surface of the socket. Reliable engagement with the inner surface of the socket is then made by the central crowned portion of each arm. Such an approach is described, for example, in Plyler et al., U.S. Pat. No. 4,169,654. The central crowned portion of each arm possesses some intrinsic flexibility which prevents excessive force concentration and wear along the pin and socket surfaces in actual contact. With the folding back of the edges of the arms, however, relative flexibility of the arms is severely limited so that the arms can be bent divergently outwardly from each other by only a small degree. It is desirable that a high degree of relative arm flexibility exists so that the arms of the pin will flex over a sufficient range to mate with different sockets that can vary in diameter.
A second approach used to counteract the creation of burrs has been to round off or coin the upper corner edges of each arm such as by pressure deformation or grinding. Pin contact arms having coined edges are shown, for example, in Lambert, U.S. Pat. No. 4,437,726. While this approach preserves the relative outward flexibility of the arms, these coined edges alone do little to prevent force concentration and the excessive wearing of the pin or socket surface materials.
A separate concern is the ability of the pin contact to adapt to longitudinal misalignment between the pin and mating socket. To address this concern, one practice has been to include a forward nose member on the contact where several elongate arms are provided extending from the rearward sleeve member to this forward nose member. This approach is shown in Henschen et al., U.S. Pat. No. 3,663,930 and Viets, U.S. Pat. No. Des. 263,219. If there is longitudinal misalignment between the pin and the mating socket before engagement, then the several arms permit repositioning or "floating" of the nose during engagement so that alignment will occur between the pin contact and the socket. Another advantage of using a forward nose member is that each arm can be outwardly bent beginning at each of its ends so that the fullest outward range of arm movement is achieved. A contrasting approach employing contacts having only a pair of arms is shown in Lambert, U.S. Pat. No. 4,437,726. Here each arm includes a reduced width portion rearwardly located on an unbent portion of the arm. The portion of the arm forward of this reduced width region can therefore be laterally twisted in a skewed direction from the portion of the arm rearward of this reduced width region to enable engagement of the forward arm portion with a socket in skewed misalignment with the pin contact.
Accordingly, it is an object of the present invention to provide a pin type contact that provides good electrical reliability upon engagement despite burr creation during stamping of the contact, that retains a high degree of arm flexibility both to reduce excessive surface wearing and to engage sockets that can vary in diameter, and that is relatively inexpensive to fabricate.
A further object of the present invention is to provide a pin type contact that is of one-piece construction and that adapts to misalignment between the contact pin and the socket.